All mirror-less cameras suffer the short/tilted ray problem, from Leica M, M43, X, Nex, and now A7X. Leica deals it with the tilted micro-lens, now rumor is, A7x is following the same trick. It's much less a problem if simply keeping a longer flange distance. For DSLR, it's given.
I compared Zeiss G series lenses vs. its SLR (Contax Zeiss) series. The G series of similar focal length, such as 35-70mm or 28mm prime, is not as good as the SLR series although it's much lighter and cute. So I concluded size does matter, and the bigger size the easier to achieve better IQ.
Leica M has the need to reduce the lens size mainly due to the range finder-blockage. It's a necessary trouble and also its uniqueness.
It's understandable that Leica M, an century old legend, has that need. But why A7x follow that is a stupid mystery to me.
What's the point? why not just give it enough flanger distance. Simply because it's a mirror-less does not require a troublesome flange distance. For the perception of size? Any image quality advantage over a DSLR?